Benthic microbial fuel cells (BMFC) have been shown to provide persistent power from sediment in both fresh and saltwater conditions. This technology allows persistent sensors to be used in remote or hazardous locations where energy is not readily available. BMFCs are able to generate electrical energy through microbial oxidation of organic compounds in the sediment. In all previous embodiments of BMFCs, oxidation of organic compounds in the sediment has to be coupled with oxygen reduction in the overlying water column. While cathodes can be made trawl-resistant or low-profile, their presence above the sediment surface creates some risk of detection or damage by trawlers or bottom-scouring activities.
During deployments, BMFC electrodes buried in sediment are required to remain at specific electrical potential to continue to produce power. These electrodes may become ineffective or poisoned at times due to various conditions such as oxygen intrusion, electrode fouling, and biofilm disruption. The system disclosed herein employs a strategy to actively monitor and stabilize the health of a BMFC through an electronics package to determine the potential of the fuel cell. The system will isolate disrupted electrodes from energy harvesting. This allows for the electrode to recover to a potential that is useful for power production and prevents an affected electrode from adversely impacting overall energy harvesting.
Currently no systems have reported implementation of intelligent energy harvesting from BMFCs. As a result, the system in place will continue to attempt operation of the BMFC if the system is physically disrupted or if sediment conditions change. A need exists for BMFCs to have continued efficient energy harvesting even under non-ideal conditions. Some previous systems require a BMFC to have at least three electrodes, where an anode can transform into a cathode via some reconfiguration of the wiring through processor-controlled switches. Another application allows the anode or cathode size to be dynamically adjusted to optimize BMFC operation. That design also requires at least three electrodes.
The embodiment described herein does not attempt to reconfigure an anode to cathode or vice-versa. This embodiment is designed to work with systems having only two electrodes (an anode and cathode) or variations could include multiple anodes or cathodes. This embodiment is designed to merely disconnect an electrode from the system once the fuel cell reaches a certain operating voltage. This protects the anode or cathode from operating under poor conditions. This embodiment allows for a less complex solution with simpler electronic circuits than the previously-described 3-electrode systems. This is key for low-power operation since most commercial microprocessors require more energy than one BMFC can generate.